ch 17 Organization of Endocrine

Question 1

what are the 3 types of chemical messengers, and how do they act?

Answer 1

1. Autocrine: affect the cell that is releasing the chemical (itself).
2. Paracrine: affect their neighboring cells. This includes neurotransmitters
3. Endocrine: affect distant cells thru bloodstream. Produce a specific response in target cell.

Question 2

1. Which system releases neurotransmitters on nearby effectors?
2. Which system releases hormones that affect distant cells?
3. Which system uses brain structures? Are chemicals of the two systems similar? Which system utilizes G proteins?
4. Action potentials are considered ………….. modulated signals, and hormones are considered ……………. modulated signals.

Answer 2

1. The nervous system.
2. Endocrine system
3. Both systems. Yes. The nervous system.
4. frequency, amplitude

Question 3

1. • 3. What are the 3 general characteristics of hormones?
2. What type of hormone has a shorter half-life and why?
3. What type of hormones have a longer half-life and why?

Answer 3

1. Stability: they persist in the bloodstream, some more than others depending on their composition.
2. Communication: Hormones react with receptors on target cells
3. Distribution: hormones circulate by bloodstream to all tissues.
4. Water soluble hormones because plasma enzymes can degrade them.
5. Lipid soluble hormones because they’re carried by binding proteins that protect them from degradation.

Question 4

1. What type of lipid-soluble hormones are are active at target cells? Why? What must they do to be active?
2. What happens to lipid-soluable hormones that are bound to proteins when they are not needed?
3. which of the following has a longer half-life, hormones that require binding proteins or hormones that do not?

Answer 4

1. Free hormones (not bound to proteins). They’re too large to pass thru cell membranes. They must detach from the binding protein.
2. They provide a reservoir for future use.
3. hormones that require protein binding.

Question 5

1. What are the 3 types of lipid soluble hormones?

2. How are lipid soluble hormones removed from blood?

Answer 5

1. steroid hormones, thyroid hormones, and eicosanoids (from fatty acids).
2. removed by conjugation

Question 6

1. What are the 3 types of water soluble hormones?
2. Some water soluble hormones are ……… and may be removed by the kidneys quickly, while others may attach to a large …………. .
3. How are most water soluble hormones degraded?
4. Give an example of a chemical alteration that could stabilize a water soluble hormone. What would the molecule be called then?

Answer 6

1. proteins, peptides, and amino acid derivatives
2. Free, protein
3. BY their target cells when they are internalized.
4. They attach a carbohydrate, a glycoprotein

Question 7

1. What are the 3 patterns of hormone secretion over time?
2. In general, ………….. soluble hormones exhibit chronic and episodic patterns, and …………. soluble hormones exhibit acute patterns.

Answer 7

1. Chronic secretion: hormone levels are relatively constant. Thyroid.

Acute secretion: stimuli cause irregular increase. Epinephrine, insulin

Episodic secretion: stimuli cause regular increases. Reproductive hormones

2. lipid, water.

Question 8

1. Name and describe the 3 types of stimulation of hormonal release.
2. What 3 mechanisms inhibit hormone release?

Answer 8

1. Humoral Control: molecules in body fluids stimulate the release of a hormone. Ie: decreased Ca+2 levels stimulate PTH.

Neural Control: Neurons stimulate hormonal release by releasing a neurotransmitter in a synapse with and endocrine cell. Ie: Neurons in adrenal medulla release epinephrine in response to stress or exercise

Hormonal Control: one hormone causes the release of another. Ie: Releasing hormones of hypothalamus trigger tropic hormones of ant. pituitary.

2. The same 3 that stimulate release.

Question 9

1. What occurs in the negative feedback mechanism of hormone release? Is this common? Is it self-limiting?
2. What occurs in the positive feedback mechanism of hormone release? Is this common? Is it self-limiting?

Answer 9

1. A product inhibits the release of a hormone. Yes, it’s common and self limiting.
2. a product stimulates the release of a hormone. It is uncommon and needs another mechanism to stop secretion.

Question 10

1. Are hormones and the receptors they encounter are specific to one another?
2. An …………… is a drug that binds to the receptor and activates it. An ………….. is a drug that binds to receptor and inhibits it.
3. What are down regulation and up regulation?

Answer 10

1. Yes.
2. agonist, antagonist
3. Target cells can fewer or more hormone receptors on their cells depending on what is needed.

Question 11

1. What type of hormones bind receptors in the nucleus of a target cell and cause a change in gene transcription to produce new proteins?
2. What type of hormones bind receptors on cell surfaces, initiating a change in the cell, often using G-proteins?

Answer 11

1. Lipid soluble hormones.

2. Water soluble hormones

Question 12

1. How do lipid soluble hormones cause transcription and translation of specific genes? What’s an example?
2. Is there usually a delay before target cells can produce their response?
3. What limits the cell’s response to these changes?

Answer 12

1. the receptor hormone complex binds to the hormone response elements in the DNA inside the cell’s nucleus, which causes synthesis of new proteins. Aldosterone is an example as it causes changes to cell’s ability to absorb Na+.
2. Yes because new proteins need to be synthesized.
3. Degradation of the hormone-receptor complex.

Question 13

Membrane-bound hormone receptors:

1. What are the 2 ways that membrane bound receptors activate changes in their target cells?
2. The cell usually produces an …………… ………………. that ultimately causes the change in target cell activity

Answer 13

1. They activate G proteins, or they directly alter the activity of intracellular enzymes.
2. intracellular mediator (second messenger)

Question 14

About G Proteins:

1. Describe what a G protein is composed of? What is attached to the alpha?
2. How does the G protein change when a hormone binds to the receptor?
3. Now that the G protein is activated, what happens?
4. How does the whole process finish and how does the alpha subunit get deactivated?

Answer 14

1. made of 3 sub-units (alpha, beta, and gamma). The alpha bit has a GDP connected to it when inactive. The G protein floats freely in cell membrane
2. The G protein attaches to the receptor, and the GDP that’s attached to the alpha gets replaced by GTP hence activating it.
3. The G protein detaches from the receptor. The alpha with its GTP detaches from the G protein and goes on to cause the cell’s response.
4. All returns to it’s original state when hormone detaches from receptor. Inactivation of the alpha happens when a phosphate is removed from the GTP going back to GDP.

Question 15

1. Name 3 ways that G proteins can cause the intracellular response.
2. What does adenylate cyclase do?
3. What does Phospholipase C do?
4. What does opening ion channels do?

Answer 15

1. Activation of adenylate cyclase, production of other second messengers like Phospholipase C, and opening ion channels.
2. produces the second messenger cAMP which activates protein kinases which phosphorylate cellular proteins.
3. degrades membrane lipids into DAG and Inositol triphosphate
4. Ions enter cell and activate proteins like calmodulin

Question 16

1.- 3. Aside from activating G proteins, what are 3 other ways that membrane-bound receptors activate change in the target cell?

Answer 16

1. They can directly activate intracellular mediators
2. They can phosphorylate intracellular proteins
3. Directly alter the activity of intracellular enzymes.

Question 17

Signal Amplification:

1. The rate of change in a target cell depends on what?
2. What do nuclear receptors need to do to initiate change in the cell? Does this make their response slow or fast?
3. What type of receptor elicits a cascade from a single hormone?
4. Describe the cascade:
5. What is amplification (the cascade effect) good for?
6. What types of receptors are good for long term processes (like pregnancy)?

Answer 17

1. On the mode of activation (ie: nuclear activation vs. second messengers)
2. They need to synthesize mRNA to create the needed proteins for the change. It makes them slower.
3. Membrane bound receptors.
4. one hormone molecule makes many second messengers which make many final products contributing to the cell’s response.
5. Immediate responses. Think epinephrine.
6. nuclear receptors